Since the introduction of the bilateral sagittal osteotomy (BSSO) for correction of mandibular prognathism and retrognathia, numerous modifications have been adopted to lessen the impact of the procedure on sensorimotor function. Immediately after surgery, most patients experience gross sensory deficits within the distribution of the inferior alveolar nerve. Although some patients clearly experience a gradual recovery of sensory function over a period of months to years, neither the incidence or degree of sensory disturbance, nor the time course of recovery of sensation have been established with any reliability. One major factor which continues to impede progress in this field has been the lack of reliable, sensitive, and quantitative techniques for evaluating the residual cutaneous sensibilities of this patient population. This study proposes to assess somesthetic function in twenty candidates for bilateral sagittal split osteotomy. Directional cutaneous kinesthesia will be assessed before and periodically after surgery using precisely controlled moving tactile stimuli and sensitive paradigms enabling the collection of data amenable to statistical analysis. Tactile detection will concurrently be assessed in order to evaluate the working hypothesis the more complex aspects of somesthesis are more sensitive to surgical trauma to the inferior alveolar nerve, and that reliable tests of these complex sensory capacities will lead to functionally and clinically meaningful interpretations of the defective neural mechanisms.